This application claims the priority of 196 49 770.1 filed in Germany on Nov. 30, 1996, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a supporting disk for a supporting disk bearing of open-end spinning rotors, said supporting disk comprising a disk-like metal base body and a thin plastic running ring, whose outer diameter amounts to at least 75 mm.
In German published patent application 38 26 851 C2, which describes a supporting disk of this type, it is given that the heat load of the plastic running ring increases with increasing width of the running surface and with decreasing outer diameter of the running ring. At the same time it is disclosed that the mechanical load, caused by the pressing of the rotor shaft, decreases with a wider running surface and increases with a larger outer diameter. Arising out of these two opposing tendencies, a compromise is disclosed for the known supporting disk with respect to the dimensional ratios, whereby with an outer diameter of 78 mm and a thickness of the running ring of 4 mm, the width of the running ring--after deduction of 1 mm for a cooling groove--should measure at least 8 mm.
In U.S. Pat. No. 4,916,891 supporting disks are disclosed which, at an outer diameter of the running ring of 70 to 80 mm, may have no cooling groove, as long as the base body is made of a good heat conducting material and the thickness of the running ring does not measure more than 3 mm. From the details given in the publication, a width of the running ring of 10 to 12 mm at the given values can be indirectly ascertained.
It is an object of the present invention to optimize further a supporting disk of the above mentioned type and in particular with regard to the undesirable heat build up of the running ring, to make the supporting disk more resistant, without a cooling groove being absolutely necessary.
This object has been achieved in accordance with the present invention in that the width of the running ring measures at most a tenth of its outer diameter.
It has been shown that by using a metal base body, that is, one which conducts heat well, and a relatively thin running ring, a so-called cooling groove, that is, a circumferential groove in the running surface, can as a rule be omitted even at high speeds of over 130,000 rpm, when the width of the running ring is sufficiently narrow, measuring preferably only 5 to 7 mm. While up to the present, mechanical loads were taken up by the widest possible running ring, and the heat load was kept to acceptable limits either by means of a cooling groove or a particularly thin coating, in the present invention the supporting disk is made as narrow as possible, whereby the heat load is obviously unable to reach a certain maximum in the first place. Nevertheless an additional cooling groove can provide further improvements if required.
The thickness of the running ring measures approximately 4 mm. This is on the one hand thin enough to transport heat quickly over the base body, and on the other thick enough to provide sufficient damping for the supportable shaft of the open-end spinning rotor. In the case of the given dimensions, an anchoring groove between the base body and the running ring can, in many cases, be omitted.
The carrying off of heat can be improved when turbulent air streams are avoided as far as possible on the supporting disk. For this reason, it is provided in a further embodiment of the present invention that the supporting disk has a smooth closed front surface, which is preferably slightly crowned.